The present invention relates to an image forming apparatus for an electronic picture copying machine or the like based on a digital system in which adjustment of image quality can be made by switching a gradation conversion table xcex3 or a color conversion coefficient or other parameters for each image quality mode, and more particularly to an image forming apparatus which can output images so that images for each mode can easily be checked.
Image forming apparatuses based on the conventional technology include a so-called copying machine for forming a image based on a read image, and a so-called printer for forming an image according to image data inputted from the outside, and for instance, in a color copying machine based on a digital system, there is provided a monitor copy mode in which an image is copied by a plurality of sheets side by side on one sheet of paper by changing a color tone of a portion thereof. The technology is disclosed, for instance, in Japanese Patent Laid-Open Publication No. HEI 1-232878.
In this type of color copying machine, prior to start of a copying operation, an operator selects a monitor copy mode and specifies a portion of a document, generally a portion especially remarked for reproduction of the colors, when a plurality of monitor images intentionally having been subjected to color correction for slightly emphasizing, for instance, yellow (Y), magenta (M) and cyan (C) respectively are formed on one sheet of paper together with a monitor image with a standard color tone with the portion not having been color correction, so called a not-adjusted monitor image.
In cases of pictures, printed materials, documents written with a fluorescent pen, even if the colors look identical to human eyes, sometimes the colors become largely different when actually copied. This phenomenon occurs because the color materials such as a photo-sensitive material, printing ink, or toner are different. In a digital image forming apparatus such as an electronic picture copying machine, to reproduce excellent images each with an image quality higher than a specified value, various types of processing such as xcex3-correction, color conversion, filter processing, and gradation processing can be executed in each mode such as a character mode and a picture mode.
Also the invention disclosed in Japanese Patent Laid-Open Publication No. HEI 6-334854 is known as a color copying machine having the monitor copy function as described above. The color copying machine with the motor copy function as described above according to this invention comprises a manipulating unit for specifying a degree of color correction appropriate for color tone of a particular portion of an image and a color correcting unit for executing color correction at a degree specified by the manipulating unit.
An RGB gradation conversion table loaded, for instance, in a color copying machine is based on a set of three colors R, G, and B because of restrictions for cost. For this reason, to respond to various types of document, such image processing parameters as a color correction (color conversion) coefficient, a space filter, and a YMCK gradation correction table are prepared, and an image quality mode corresponding to a type of the document is selected.
As this type of invention, for instance, the invention disclosed in Japanese Patent Laid-Open No. HEI 6-86068 is known, and this invention comprises a coincidence detecting circuit for subjecting image data read by a reader to density correction by referring to the xcex3-correction table, outputting the corrected image data, and also outputting a coincidence signal when positional information indicating a position of the read image is coincident to positional information from a position specifying unit for specifying an arbitrary position or an area on a document and outputting the positional information; and a xcex3-correction circuit for subjecting the image data read by a reader to density correction according to xcex3-correction data, outputting the corrected image data, and switching, when the coincidence signal is inputted from the coincidence detecting circuit, xcex3-correction data to xcex3-correction data according to the density information specified by the density specifying unit for executing density correction, and the RGB gradation conversion table is switched for each current area.
On the other hand, as documents to be copied by a color copying machine or the like, in addition to characters and pictures, there are various types of documents such as a silver-salt picture such as a glossy photo (development paper), a printed document, a document printed with an ink jet, a document written with a fluorescent pin, a map, or a thermally-transferred document. In the conventional type of color copying machines, when documents to be copied (types of paper or color materials to be used) are different, an appropriate image quality mode is selected from a plurality types of image quality mode prepared in the copying machine, and optimal image processing parameters most suited to each document are used to obtained an image more faithful to the document. As described above, by preparing various image processing parameters such as a space filter, a gradation conversion table, a dither, and a color conversion coefficient as an image quality mode, a user can set conditions most suited to a document by executing a simple operation of selecting a mode.
In the actual situations, however, even the same type of documents are prepared by various types of printers. Because the printers are produced by different manufacturers or color tastes of used color materials are different, and further the dither processing or a resolution of each printer are different, some times a copied image may not be a desired one in terms of faithfulness for a document according to the same image processing parameters.
To solve the problems as described above, disclosed in Japanese Patent Laid-Open Publication No. HEI 8-58158 with the title of xe2x80x9cColor Adjusting Apparatusxe2x80x9d is the technology for obtaining a copied image desired by an user by executing color correction specified to each ink jet manufacturer.
With the conventional type of technology as described above, although there is provided an image quality mode for reproducing colors of different color materials such as those used in pictures, printed materials, or documents printed with an ink jet, in a case where a plurality of color conversion coefficients are available for one image quality mode, how image quality adjustment was executed can not be confirmed unless actually copying is executed each time an image quality mode is selected and the copied image is checked. For this reason, it is required to execute printing for trial many times for selecting appropriate image quality mode, which requires many sheets of paper or a large quantity of toner to be consumed, and also along time and much energy are required.
More specifically, although there are various types of documents in addition to characters and pictures such as silver-salt pictures such as a glossy photo (development paper), printed documents, those printed with an ink jet, those written with a fluorescent pen, maps, and thermally-transferred documents, when types of documents to be copied (types of paper or color materials to be used) are different, by using a gradation conversion table, dither, and a color conversion coefficient most suited to each document, an image more faithful to the document can be obtained. For this reason, by previously preparing a gradation conversion table, a dither, and a color conversion coefficient for each (image quality) mode, an user can set conditions most suited to a document by executing a simple operation of selecting a mode. However, sometimes the selected mode may not satisfy the user""s intention. In this case, sometimes an excellent image is obtained in other mode, but if it is tried to output an image for each mode, the work load becomes high and a long time is required, which is disadvantageous.
Also in color copying machines based on the conventional technology, various types of image quality mode are available. The mode includes, for instance, those for each of which image processing parameters are set to respond to various types of documents such as a printed picture such as a glossy photo, a picture on development paper, a character, a copied document, a map, a document written with a fluorescent pen, a document printed with an ink jet, and thermally-transferred document. However, a user can not easily determine to which of the document types described above a document to be copied corresponds, or in which image quality mode copying should be executed, which is very inconvenient.
Even if an image quality mode is selected, unless image processing is changed according to a manufacturer of a printer or a copying machine used for copying the document, some times an image faithful to the document can not be obtained. For instance, in cases of a document with an ink jet, a silver-salt picture document, or a copied document, unless the document is corrected according to a manufacturer and a type of the machine, an image faithful to the document can not be obtained, which is disadvantageous.
In the case as described above, even if the guidance of xe2x80x9cPlease select a mode for the manufacturer of a printer or a copying machine used for preparing the documentxe2x80x9d or the like is displayed, generally the user can not easily determine the manufacturer of the printer or the copying machine used for preparing the document. This is also true in a case of a film projector.
The color copying machine disclosed in Japanese Patent Laid-Open Publication No. HEI 6-334854 has only a function to execute color correction by specifying a degree of color correction, and the problems as described above are not solved in this color copying machine.
Also it is conceivable to output an image enabling a user to understand in which mode the image is prepared so that the user can easily determine a mode for obtaining an excellent image, but when an arbitrary area of the document to be outputted is specified by area processing, sometimes the image in the selected mode may not be accommodated within a specified form. If the image can not be accommodated within a form, the entire image can not be processed according to the selected mode. This means that, in a case of a sheet of form with a plurality of images formed thereon, different types of processing must be executed according to an area of the formed image, and this problem has not been solved in the conventional technology.
Also with the invention disclosed in Japanese Patent Laid-Open Publication No. HEI 6-334854, it is possible to specify a degree of color correction, but a mode of color correction can not be specified according to a type of a document, a manufacturer of a document, nor to a type of the machine used for preparation of the document.
On the other hand, the conditions for an excellent image desired by a user include faithfulness to the document in color faithfulness, that there is no abnormality in a copied image due to a determination error as to a character or a picture area executed automatically, and that the image is not degraded nor faded as compared to the document. However, even in a case of the same document type, faithfulness of a copy obtained according to image processing parameters specified to a particular image quality mode does not always satisfy the user.
For instance, in a case of a document printed with an ink jet printer, as a color taste of a document or a dither processing varies according to each manufacturer of the printer, faithfulness of a copy prepared according to the same image processing parameters specific to the particular image quality mode does not always satisfy the user""s needs. Also there is a printer in which a resolution or a dither processing can be changed according to setting of the printer and 4 to 6 colors are available for printing, and faithfulness of a copy according to the same image processing parameters specific to the particular image quality mode does not always satisfy the user""s needs.
Further a CCD output vale for read balance for R (Red), G (Green), and B (Blue) with a CCD (Charge Coupled Device) in a conventional type of scanner is adjusted so that values for R, G, and B will be substantially identical when a document painted with achromatic-color ink is used and the achromatic-color document is read. When an achromatic-color document formed on common paper is read with a scanner set as described above, read values for R, G, and B are identical, the document is read as an achromatic-color document, and the faithfulness of color is excellent even when a chromatic-color document is read.
In contrast, when an achromatic-color document printed, for instance, on development paper used in the silver-salt picture system is read by a scanner with the CCD output balance adjusted as described above, output values for R, G, and B are not identical, and an output signal for Red may be detected as a lower value as compared to the actual value. This type of phenomenon is generated when a reflection factor in a long waveform region of a visual light area on development paper is low. As a result, a cyan color factor is rather emphasized in an obtained copy. The tendency varies according to characteristics of a spectral transmittance of a CCD, performance of a spectral transmitting filter provided on a light path from a document to the CCD, or the spectral reflection characteristics of the CCD.
An example of an achromatic-color copy was described above, but the same is true also in a case of chromatic-color copy, and it is often observed, for instance, during adjustment for printing, that a copied image with a color taste different from that visually observed is formed in a case of the document on development paper. In the case as described above, generally a color correction factor or a YMCK gradation factor correction table is changed according to a type of a document, but sometimes the faithfulness of color in an obtained copy is not satisfactory.
It is possible to prepare many gradation correction tables used for subjecting image data outputted from an image reader to gradation conversion for executing sufficient correction, but this kind of configuration causes increase in cost. The reason is as follows. Namely, in an image forming apparatus based on a system in which Y, M, C, K images are successively formed on a light-sensing body and the Y, M, C, K images are overlapped on a transfer body, only image data for one of Y, M, C, and K colors is required in a YMCK gradation conversion table, in other words it is required only to provide a gradation conversion table enabling input/output of, for instance, an 8-bit signal thereto or therefrom. In contrast, in a case of a gradation conversion color for R, G, B colors, as 3 types of signals for R, G, and B colors are required in color correction processing in a subsequent step, so that gradation conversion tables for three colors of R, B, and G colors are required for both input and output. For this reason, there is no way but to use a circuit with a larger scale for preparing a memory space for a plurality of image areas on one sheet of a document, which causes cost to increase.
If the configuration is employed in which a plurality of gradation conversion tables used for gradation conversion of image data outputted from an image reader are provided and an appropriate gradation conversion table is selected for use according to an image area inside a document, the image quality is improved, but the necessity of providing a number of gradation conversion tables causes cost to increase.
Further, as gradation conversion characteristics varies according to a document type, unless an appropriate gradation conversion table is employed according to a document type, faithfulness of a reproduced image in colors to the document may be rather low.
It is a first object of the present invention to provide an image forming apparatus in which a monitor image for selection of image quality mode suited to each individual document can be formed, and a user can select a mode suited to a document after the user visually checks the monitor image.
It is a second object of the present invention to provide an image forming apparatus in which a user can easily select an image quality mode suited to each discrete document by visually checking monitor images.
It is a third object of the present invention to provide an image forming apparatus in which a user can execute color correction according to such a parameter as a document type, a manufacturer of a document, or a machine type.
It is a fourth object of the present invention to provide an image forming apparatus in which a desired copy can be obtained from various types of document.
It is a fifth object of the present invention to provide an image forming apparatus which can insure faithfulness of a copied image in terms of color to a document irrespective of a document type, nor to parameters set for printing.
It is a sixth object of the present invention to provide an image forming apparatus which can insure faithfulness of a copied image in colors to a document without causing cost increase.
The forming apparatus according to the present invention comprises an image reader for reading image data by optically scanning a document image placed at a reading position; an image processor for receiving image data from the image reader and subjecting the image data to image processing; an image forming unit for forming an image on a transfer material based on the image data having been subjected to image processing by the image processor; and a particular area setting unit for setting an arbitrary image area in the document image as a particular area; wherein the image processor receives, when the particular area is set by the particular area setting unit, image data corresponding to the particular area, generates a plurality of monitor image data having been subjected by setting a different image quality mode for each data respectively; and the image forming unit receives the plurality of monitor image data, allocates each monitor image data at a different position on the same transfer material respectively, and forms a plurality of monitor images on the same transfer material, and for this reason there is provided the effect that images for particular areas (monitor images) each processed in a respective different image quality mode can be formed at different positions on one sheet of form so that an image for each mode can easily and visually be checked and an appropriate mode can easily be selected.
Other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.